I know it's something of an old topic, but I hate to see it go unanswered, so...
It appears that BD recording (along with DVD recording) is currently supported by userland tools without need of explicit support in the kernel. (
A bit more information on that.) So there you go, it should work right now. It was working since (at least) August, it seems. (Of course, you might want to check on this yourself, if you've got a BD drive around.)